57-13-08 PIPER: Applies to Model PA-23 Serial Numbers 23-1 to 23-729, Inclusive.
Compliance required by September 1, 1957.
To prevent inadvertent retraction of the landing gear due to malfunction of the landing gear hydraulic system, install an antiretraction device (Piper Kit No. 754140 or equivalent) that will prevent start of the retraction cycle and consequent landing gear collapse while the aircraft is on the ground.
(Piper Service Bulletin No. 145 of December 31, 1956, covers this subject.)